Telephone transmitter



latencia Aeg. 13, 1929.1

[UNITED STATESY PATENT-OFFICE.

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TLEPHUNE TRANSMITTER.

Application med .Tune 11,

i f to transmitters in which the microphone ele- 35 granules for the current to travel across..

. currents through low resistance 1 44) encountered in previoustransmittexs.

nient is of the carbon granulartype.

Vs It is an object of the invention to desi a transmitter for use in the soca1led cra le or hand type of telephone and the principalobject is to design a transmitter or this type that will operate satisfactory regardless' of 4 1c the position that it may beheld 1n when use.

Another object of the invention is the provision of means whereby relatively low values of current may be em loyed w1thout detracting in 'any way from t e satisfactory operation of the transmitter.

In accordance with these and other objects, not specically'mentioned, but which Vwill be readily apparent from the detailed 2o descri tion, the electrodes 'of the microphone have n placed comparatively 4close together. They are of` thelsame small diameter and area so as to 'concentrate the current across the 'intervening space between the electrodes, this space being lledvwith the comminuted material. Y y ,n

A feature of the vinvention resides fin ap` plying' a flat insulatingring -around t e eri hery of each electrode, andmountin 3@ it wlth the electrode onto a metal stud.

` relatively large surface is therefor presented to the granular carbons so they may be agitated,l thereby eliminating packing, while the small electrodes present a small area to the This arrangement permits the'use of low current values without the losses due to stray` aths in the carbon chamber, as has been the' diiliculty The foregoing .and other useful obects are attained through means which will Jhe fully described hereafter, reference` being had to the accompanying drawings-in which Fi -1 is a rearview of the transmitter of thisinvention; Fig. 2.a cross section .along the line A-A through f the center of Fig. 1; .we Fig. 3 shows in extended form the relationship ofl the various parts and 'the so general construction-ofthe transmitter buter'sprin is he I metal clamping ring 15.v

1927. lrtm1 No. 198,013.

ton or microphone element, with several of the parts in section.

Referring to Figs. 1 and 2 of the drawing the reference character 1 indicates the rin sha ed metal back plate having a meta briu piece 2 integral therewith, upon whic the microphone elements are mounted. A ring shaped face plate 3 screws into a threaded flange around the periphery of the back plate 1 and holds the diaphragm 4 in place. The foregoing comprises essentially the means for mounting the transmitter, and 4while the usual rear metal casingor covering for the transmitter and 'heavy metal face plate and mouth piece have not been shown, it isvery readily conceived how these .parts 4 may be attached.' While this embodiment' of the invention was conceived primaril for ahand or cradle telephone it may readi y be adapted for other uses than that shown, by anyone skilled in the art. t

The metal diaphragm 4 is slightly turned 4 out at its periphery and its edge rests against a'pair of rings 31 made of` insulating material and laced 1n the face plate 3 so as 4'I5 to cushion' t e diaphragm 4 on the transmitter casing. The face plate 3 forces the rings 31 a inst the diaphragm 4 and holds the diap ragm under constant tension. The dia-l phragm 4 is mounted between two locking nuts 8 on the stud 12. A-leg of the damper spring 6 is insulated from and extends on' each side of the diaphragm 4 so as to dampen' any excessive speech vibrations. This dam din place on the plate 5 y a air o screws, on the plate 1. Y

he microphone elements consist essen tially of a 11191531 cup 16 provided with exterior screw threadsA ada ted to receivea etween this rin and the edge of the cup 16 there is clam the' metal auxiliary diaphragm 11, toget er with the annular paper ring 26, which takes upanyirregularities in the surfaces between the metal diaphra `11 and the clampin ring 15. The meta stud 12, has the polishe facecarbon electrode 13 suitably fastened to the enlarged face of the stud, and has an annmlar ring 14 of insulating material surlrounding the edge of the electrode 13, also electrode of the same diameter, which is suitably mounted on the enlarged face of the metal stud'18. Surrounding the edge of the electrode 2O and'also fastened to the stud 18 is an annular insulating ring 19 slightly larger than the surface of the stud 18 and similar to the ring 14 of the other electrode 13. Another insulating ring 30 Vis held against the rear surface of the stud 18. Attached to the inside cone shaped surface of the metal cup 16 is a lining 17 consisting of insulating material. The stud 18 rests against the small end of the cup 16, the insulating lining 17 and the ring 30 insulating it therefrom. It will thus be seen that the stud 18 is completely insulated from the chamber formed by the cup 16, and in no way can the fine carbon granules contained therein reach it. The stud 18 is clam ed to the bridge plate 2 by a nut 24 and this stud Which has an insulating bushing 21 surrounding it, also supports the cup 16, the metal ter- `minal plate 25, the insulator 27 and on the top of the bridge 2, the insulator 22 and terminal plate 23. Theterminal plates each have a screw 28 and 29 to which the Wires of the transmitter are attached.

By referring to Fig. 3 it will be apparent how the microphone element is assembled.

i The stud 12 containing the metal diaphragm l1 onv the rear of the enlarged face of the stud, and the insulating annular ring 14, surroundin the small electrode 13, on the front, is placed in the clamping ring 15, with the annular spacing ring 26 between the metal diaphragm l1 and the clamping ring. The metal cup 10 is clamped to the diaphragm on the stud 12 by the nut 9 so that the periphery of the cup will coincide withthe periphery of the enlar edface of the stud on t e-opposite side of t e diaphragm. This is so that ,thatdiaphragm will not buckle or' bend. The stud 18 with the annular insulating ringBO on the rear of its enlarged,

face, and the annular insulating ring 19 surrounding the electrode 20 on its front, is

assed through the hole of the cup 16. This liole is made large enough so that the stud will not touchfthe sides. It will therefor be seenthat this stud 18 is completely insulated from the cup 16. After the stud 18 and the cup 16 are mounted on the bridge piece 2, the clamping ring 15 is screwed onto the cup4 and the unit is then complete.

The electrical circuit of this transmitter is as follows: from the terminal 28, throughA the terminal plate 25, through the cup 16 ery of the flat face of the stud 12,

to the metal diaphragm 11, through the stud l2 to the electrode 13, and thence through the comminuted material to the electrode 2() and the stud 18. From the stud 18 the current passes` to' the terminal plate 23 to the terminal 29. From the above traced circuit it will be noted that the cup 16 is completely insulated from the stud 18.

The foregoing describes one embodiment of the invention and it will be seen by referring to the drawings that the electrodes 13 and 20 which are placed'relatively close together are of a smaller size than have been used heretofore. Due to the small space between the electrodes, occupied by the comminuted material, lwhich is also the Apoint where the greatest agitation of the granules takes place, relatively low values of current can be used in this transmitter, while the 'sloping cone shaped walls of the cup 16 assists in restricting the carbon granules at theV point Where the-greatest percentage of agitation takes place. This considerably reduces the tendency of the carbon to pack. 'lhe insulating annular rings 14 and 19 around the electrodes, concentrates the current directly onto the electrodes, and ring 14 on the stud 12, which is connected directly to the main diaphragm 4 and therefore responds to any sound vibrations impinged thereon, agitates practically the whole mass ofthe comminutedmaterial and no-low resistance leakage path for the current is formed. This would be practically equivalent to having large'electrodes to agitate the granules, but in this case'the electrodes are comparatively small so that the maximum amount of resistanceiis obtained across the electrodes.

The exposed surfaces around the periphand also part of the auxiliary diaphragm 11, which are in direct contact with the carbon granules, form a means whereby a reserve supply of granules is kept, but due to the comparatively long distance for the current to travel to the electrode 20 and the resistance of the granules between, there will be veryv little if no currentiow over this path..

The conical shape of the electrode chamber and the exposed surfaces described in the above paragraph and around the periphery of the electrodes eliminates any possibility, of the ltransmitter being o en circuited, irrespective of the position o it when in use.

Having` described this invention, what is considered new and what is desired to have is pointed out lar rin s on saidstuds around said electrodes or insulating said studs from said comminuted material, means for moving one of said studs to agitate said comminuted material, a maximum'amount of movement taking place between said electrodes, while the surfaces of said studs covered by said annular rings agitates said material an amount to prevent packing thereof and always' keep the space between said electrodes filled with said material.

2. In a telephone transmitter, an electrode chamber containing comminuted material, a pair of opposite spaced .metal studs projectlmg into each end of said chamber, an electrode on each of said studs also projecting into said chamber, said electrodes spaced apart in said chamber a smaller amount than said studs, annular insulating rings around said electrodes on said studs projecting into said chamber a lesser amount than said electrodes but a greater amount than said studs, means for moving one of said studs to agitate said comminuted material, a greater amount of agitation taking place between said electrodes and a lesser amount between the insulated rings on said studs so as to assist in maintaining all of said comminuted material in constant ino--y tion. 3. In a telephone transmitter, an electrode chamber containing comminuted material, a pair of metal studs mounted opposite each other in each end of said chamber, said studs each having a flat annular surface etending into said chamber, annular insulating rings on the surface of each stud extending into said chamber, an electrode inside said annular ring and on each stud and projecting into said chamber beyond the edge of said ring, means for agitating the whole surface of one kof said studs in said chamber to` agitate said comminuted material, the insulated ring on the surface of each stud agitating said material an amount to prevent packing thereof, while the maximum amount of' agitation occurs between the surfaces of said electrodes.

4. In a telephone transmitter, an electrode chamber containing comminuted material, a metal stud closing one end of said chamber and having a large surface extending into the chamber, a small rear electrode projecting from said stud into said electrode to insulate said stud from said comminutedmaterial, amovable diaphragm closing the opposite end of said chamber, a second stud mounted on said diaphragm in said chamber and having a large surface therein, a small front electrode projecting from said second' stud yinto said chamber, an annular insulating ring surrounding said front electrode on said second stud, means for moving said diaphragm to agitate said comminuted material, the maximum amount of movement Ataking place between said electrodes, while the large insulated surfaces on the studs around' said electrodes assists in said movement to agitate said material to prevent packing thereof and restrict the flow of current only "between said electrodes.

ln witness whereof, I hereunto subscribe my name this 9th day of June, il. D. 1927.

ALBERT E. WOODRUFF 

